What servo would you reccomend to use with the Sharp IR Sensor for 180 degrees? I know the HS-311 is popular for the $50 robot, but if you had to do it again - would you make the same decision? What servo does hyper squirrel use?

Well I use the HS-311 on hypersquirrel cause its cheap and I have tons of them.

Ideally you want one with a really high rotation speed (torque doesnt matter). Bigger servos are slower when changing direction (higher momentum), so you probably want small servers with high speed ratings.